Why is sushi so popular?
Because it was well marketed in the West. There are many foods just as delicious as sushi that are not as popular. You notice how many people claim that it is healthy? This is only true if the fish is extremely fresh (as it tends to be in Japan), But if it is past its prime, the sushi is not healthy at all, and this is probably the case in at least half of all sushi joints. So you see how the positive marketing has left its mark in the minds of many, reality to the contrary notwithstanding. The trendiness of a food outweighs almost everything else.